This invention relates generally to medical devices which are implantable in the human body. More particularly, the present invention relates to a subcutaneously implantable direct delivery access port for repeated intermittent injection, which may be used in connection with a subcutaneous drug infusion apparatus.
Some medical treatments, such as chemotherapy, require repeated introduction of chemical substances into a patient's body. Often these chemical substances are introduced into a specific body site. Earlier, it was typical for such chemicals to be introduced by intravenous injection through the patient's skin into a vein. Such repeated venipuncture injections are painful and often difficult, especially with elderly patients. Additionally, some drugs are highly reactive and so traumatic to small peripheral veins that the veins cannot tolerate multiple injections. Also, such intravenous injections are often undesirable because the need for controlled long term introduction cannot be attained.
In order to overcome some of the drawbacks associated with repeated venipuncture injections, implantable infusate injection ports have been developed which typically include an internal chamber, a penetrable self-sealing septum, and a hollow male outlet connector, all of which are implanted subcutaneously within the patient. Such injection ports provide a permanent injection site without immobilizing the patient.
Normally a device of this type is surgically implanted in a patient so that it is positioned beneath the skin with the septum facing outwardly. Often the outlet connector is attached to a catheter element for transmitting fluids to a predetermined area of the patient's body, such as a large vein. Once an injection port of this type has been installed in a patient, the internal chamber can be periodically filled with medication by inserting a hypodermic needle in the patient so that it penetrates the skin and passes through the septum for injecting medication into the internal chamber. It has been found that injection ports of this general type can be effectively utilized for dispensing medication in the body of a patient over a prolonged period of time, and that it is generally preferable to a catheter or the like which would require a permanent opening in the skin.
Subcutaneous injection ports can also be used for the administration of medication to a patient. For example, in many therapeutic procedures there is a need to implant a drug delivery device. Such an implantable drug delivery device provides a bolus or therapeutic dose of the drug contained therein to a particular location within the patient's body. In order to replenish the drug in the implanted device, a self-sealing subcutaneous injection port can be provided in fluid communication with the drug delivery device. An exemplary drug delivery device is shown in U.S. Pat. No. 4,681,560, the contents of which are incorporated herein by reference. The subcutaneous injection port provides a means for administering additional medicament into the device as the medicament can be injected using a syringe inserted subcutaneously into the injection port without the need for a subsequent surgical procedure.
Depending on the drug delivery device, it may be extremely important, and even critical in some instances, that small foreign substances introduced into the injection port be kept from passing to the delivery device and, ultimately, to the patient. Particulate foreign substances may be inadvertently "picked-up" as the needle is pushed through a patient's skin just prior to insertion into the injection port. Filters have been utilized to screen out undesirable small particulate foreign matter prior to the injected fluid being allowed to exit the injection port.
In using subcutaneous injection ports for the injection of drugs, great care must be taken to insure that the hypodermic needle punctures the septum and is not deflected away by the supporting structure so that the drug is accidentally introduced into the subcutaneous pocket within which the device is located. As mentioned above, with certain drugs this type of extravasation can be extremely serious. Moreover, certain prior art devices tend to leak around the puncture site, or around the internal reservoir of the device, particularly under conditions of back pressure experienced during the injection step.
Accordingly, there has been a need for an improved subcutaneous injection port of simplified construction and having an assembly process which virtually eliminates any possibility of leakage from the internal chamber. Additionally there exists a need for such an improved injection port which presents a unitized elastomeric exterior, wherein the septum is integrally formed with the body of the port. This again would tend to minimize fluid leakage. Further, such an injection port is needed which provides adequate compression of the septum about its periphery between at least two rigid members. Preferably these rigid members would not have surfaces exposed exteriorly of the injection port, with the possible exception of an outlet connector. The assembly process should preferably maximize use of interference fittings between components, and minimize any requirement for the use of adhesive sealants or other time consuming manufacturing steps. The present invention fulfills these needs and provides other related advantages.